854 Prof. Allman on the Construction and 



Medusa at the time of liberation deep bell-shaped ; manubrium 

 not reaching the orifice of the bell, and having its mouth sur- 

 rounded by four short tentacles; radiating canals four, each 

 terminating distally in a bulb, from which are developed two 

 tentacles, each with a distinct ocellus at its base. 



Corynopsis Alderi, Hodge {sip.), = Podocoryne Alderi, Hodge. 



The genus Corynopsis has been constituted for the Podocoryne 

 Alderi of Mr. Hodge— a Hydroid, however, whose gonosome will at 

 once separate it from the true Podocoryncs. It will be noticed that 

 the Medusa, at the time of its liberation, is not to be distinguished 

 from that of Bougainvillia at the same stage of its development. 

 The further progress of the Medusa of Corynopsis has not been 

 traced ; but it is highly probable that we have here a true case of 

 isogonism with Bougainvillia. 



4. DiPLURA, Greene> MS. 



Trophosome. — Polypite supported on the summit of a simple 

 hydrocaulus, with a branched and creeping (?) hydrorhiza ; 

 periderm?; tentacles filiform, in a single verticil (?) near the 

 distal extremity of the body. 



Gonosome. — Gonophores phanerocodonic, on simple peduncles, 

 which arise in a verticil from the body of the polypite at the 

 proximal side of the tentacles. Medusa deep bell-shaped, with 

 moderate-sized manubrium; radiating canals four, each termi- 

 nating in a bulbous expansion at the point of intersection with 

 the circular canal : from one of these marginal bulbs two long 

 tentacles are developed ; the rest of the margin is destitute of 

 tentacles. 



The genus Diplura was originally, under the name of Diplonema, 

 estabhshed by Prof. J. Reay Greene for a Hydroid of which the Me- 

 dusa was alone known to him. (Nat. Hist. Rev. 1857, vol. iv.). The 

 name of Diplonema, however, happened to be preoccupied by the 

 botanist, and Prof. Greene has since substituted for it that of Di- 

 plura. The Medusa thus named he found free in the open sea near 

 Dublin; and it is undoubtedly congeneric with that described by 

 Steenstrup as the Medusa of a Hydroid trophosome, which he names 

 Coryne fritillaria. Steenstrup' s Hydroid, however, is certainly not 

 a Coryne in the sense in which we must now understand this genus ; 

 and though his description and figure are insufficient for an entirely 

 satisfactory diagnosis, they compel us to regard his Hydroid as the 

 representative of a distinct generic type, to which the name pro- 

 posed by Prof. Greene for the Medusa, whose relation to Steenstrup' s 

 form he recognized at the time of its discovery, must now be given. 



Agassiz refers it to Steenstrupia (Contr. Nat. Hist. U. S. vol. iv.) ; 

 but the genus Steenstrupia was founded by Forbes for a Medusa of 

 an entirely different type, though possessing unmistakeable affinities 

 with Diplura. 



